Oyi the Genera of the Dromiidas. 297 XXXIX. — Description of a tiew Species 0/ Balanus /rom the Collection of the British Museum. By Prof. A. Gruvel. Balanus violaceus, sp. n. Diagnosis. — Walls and base porous. Radii well deve-loped, not pierced by pores. Test violaceous in general colour, with numerous narrow, longitudinal, clear grey-blue ribs. Base entirely porous. Scuta with the articular ridge very prominent, the ridge of the adductor feebly developed and situated a little nearer the rostral than the tergal margin ; pit for the adductor muscle deep ; cavity for the lateral depressor muscle also deep. Terga with the lidge and the articular furrow very clearly marked ; spur prominent at the rounded lower extremity, and situated at a slightly less distance than its own width from the basi-scutal angle ; crests for the depressor muscle very distinct and prominent; no external longitudinal furrow, but, on the contrary, a longitudinal ridge ; apex slightly projecting, terminating in a blunt point. Habitat. Unknown. N.B. — This species comes near to B. nuhilus, Darwin, and consequently its place is in section C. XL. — On the Genera of the Dromiidte. By L. A. BORRADAILE, M.A., Lecturer in Natural Sciences at Sehvyn College, Cambridge. Since Bouvier's paper " Sur I'Origine homarienne des Crabes " (Bull. Soc. Philom. 1896) the limits of the genera of this family of primitive crabs have become very uncertain. In the list of genera and species of the Dromiacea which he has lately published* Alcock has included Slimpson's Dromidia^ with Dromia as a subgenus, and placed Dromidiopsis '\ with Dromidia as synonymous, regarding Cryptodromia, Stimps., as still an independent genus. In working out the collection of Dromiidyj made by the late Maldive Expedition I have been led to conclusions which differ from these with regard to the genera Dromidia and Dromidiopsis and support the view hitherto held of their generic distinctness. More-over^ it has seemed that certain other rearrangements are * ' Catalogue of the Indian Decapod Crustacea iu the Collection of the Indian Museum,' part i. fascic. 1, pp. 74-80 (1901). t Borradaile, P. Z. S. 1900, p. 572.
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